The Bacterial Diseases of the Bean 25 



Cultural characteristics 

 (All cultures incubated at 27° C. unless otherwise stated) 



Beef-extract agar slants (pH 7.0). In twenty-four hours there is fair yellow 

 growth along the streak, which by the third day becomes abundant, 

 filiform, wet-slimy, and mustard yellow in color; the color is denser in 

 the center and is pale and watery at the edges. The consistency of the 

 culture is frequently watery to thin butyrous. On the second day a 

 slight purplish color is noticeable in the medium. This gradually deepens 

 through a brownish purple to a deep brown. The rate of formation of 

 this pigment appears to vary somewhat with the medium. 



Beef-infusion agar slants (pH 7.0). Growth is similar to that on beef- 

 extract agar. The coloration of the agar varies with the lot of media 

 used, from a light to a very deep brown. On one lot which colored very 

 rapidly, the viability of the organism was lost within a week. 



Beef-extract agar plates (pH 6.9). Colonies two weeks old are approxi- 

 mately 1 centimeter in diameter, are honey yellow in color, and often 

 have a zone of a watery appearance about the edge. The edges are 

 entire to slightly undulated. In consistency the colonies are watery to 

 weakly butyrous. The yellow pigment of the cells appears somewhat 

 dull, owing to the brown coloration of the medium. 



Beef-extract bouillon (pH 7.0). The broth becomes cloudy in twenty -four 

 hours. At the end of four days a light yellow ring develops and a slight 

 flocculation appears in the medium. Small bacterial islands float on 

 the surface and a yellow sediment is formed. Within a week the broth 

 becomes brown near the surface and the color gradually extends down- 

 ward. At the end of three weeks the medium is a dark brown through- 

 out and the cloudiness of the culture clears to a considerable extent. 



Gelatin stab (pH 6.6). (Temperature 21° C.) In twenty-four hours there 

 is a light growth along the stab. Liquefaction begins in three days but 

 is not complete until the end of five weeks. No consistent form of 

 liquefaction occurs. At the end of seven days a browning of the liquefied 

 medium takes place and the pigment progresses with liquefaction. A 

 heavy yellow sediment is formed. 



Milk. A yellow ring is noticeable in four days. In six days the milk is 

 yellowish, and a clearing begins at the surface and proceeds rapidly 

 throughout the tube. A heavy casein sediment is formed in the bottom, 

 which is gradually digested. The liquid above is yellow and fairly clear, 

 but later a brown color begins to appear at the surface of the medium 

 and extends downward. After six weeks or more a careful examination 

 will reveal small masses of tyrosine crystals which appear to be partly 

 digested. 



Litmus milk. A yellow ring is formed in four days, and a clearing of the 

 milk begins at the surface and rapidly progresses downward. Litmus 

 is reduced, and the liquid becomes rather muddy but later clears and is 



